Estimation of Torso Vibrotactile Thresholds Using Eccentric Rotating Mass Motors

Effects of Contact Force on Vibrotactile Perceived Intensity Across the Upper Body

Full-body haptic suits, which can provide tactile sensations across the entire body, have been gaining popularity recently. The tightness of a suit to the user's body determines the contact force between the tactile actuators and the body. The contact force is likely to alter the intended perceptual effects, but relatively little is known about the extent of the alteration. Under this context, we present the effects of contact force on vibrotactile perceived intensity on three body parts: dorsal hand, upper arm, and lower back. To this end, we conducted three perceptual magnitude estimation experiments while controlling vibration amplitude, frequency, and contact force. The results show that increasing the contact force generally made the vibration stimuli feel stronger, while the specific behaviors were dependent on the body part and the experimental variables. Finally, we summarize the major findings and provide guidelines regarding contact force adjustment for effective full-body haptic rendering.

A direct comparison of sound and vibration as sources of stimulation for a sensory substitution glove

Sensory substitution devices (SSDs) facilitate the detection of environmental information through enhancement of touch and/or hearing capabilities. Research has demonstrated that several tasks can be successfully completed using acoustic, vibrotactile, and multimodal devices. The suitability of a substituting modality is also mediated by the type of information required to perform the specific task. The present study tested the adequacy of touch and hearing in a grasping task by utilizing a sensory substitution glove. The substituting modalities inform, through increases in stimulation intensity, about the distance between the fingers and the objects. A psychophysical experiment of magnitude estimation was conducted. Forty blindfolded sighted participants discriminated equivalently the intensity of both vibrotactile and acoustic stimulation, although they experienced some difficulty with the more intense stimuli. Additionally, a grasping task involving cylindrical objects of varying diameters, distances and orientations was performed. Thirty blindfolded sighted participants were divided into vibration, sound, or multimodal groups. High performance was achieved (84% correct grasps) with equivalent success rate between groups. Movement variables showed more precision and confidence in the multimodal condition. Through a questionnaire, the multimodal group indicated their preference for using a multimodal SSD in daily life and identified vibration as their primary source of stimulation. These results demonstrate that there is an improvement in performance with specific-purpose SSDs, when the necessary information for a task is identified and coupled with the delivered stimulation. Furthermore, the results suggest that it is possible to achieve functional equivalence between substituting modalities when these previous steps are met.

Less Vibrotactile Feedback Is Effective to Improve Human Balance Control during Sensory Cues Alteration

For individuals with altered sensory cues, vibrotactile feedback improves their balance control. However, should vibrotactile feedback be provided every time balance control is compromised, or only one-third of the time their balance is compromised? We hypothesized that vibrotactile feedback would improve balance control more when provided every time their balance is compromised. Healthy young adults were randomly assigned to two groups: group 33% feedback (6 males and 6 females) and group 100% feedback (6 males and 6 females). Vibrotactile feedbacks related to the body's sway angle amplitude and direction were provided, while participants stood upright on a foam surface with their eyes closed. Then, we assessed if balance control improvement lasted when the vibrotactile feedback was removed (i.e., post-vibration condition). Finally, we verified whether or not vibrotactile feedback unrelated to the body's sway angle and direction (sham condition) altered balance control. The results revealed no significant group difference in balance control improvement during vibrotactile feedback. Immediately following vibrotactile feedback, both groups reduced their balance control commands; body sway velocity and the ground reaction forces variability decreased. For both groups, unrelated vibrotactile feedback worsened balance control. These results confirmed that participants processed and implemented vibrotactile feedback to control their body sways. Less vibrotactile feedback was effective in improving balance control.

Evaluation of Vibrotactile Output From a Rotating Motor Actuator

Specialized vibrotactile actuators are widely used to output haptic sensations due to their portability and robustness; some models are expensive and capable, while others are economical but weaker and less expressive. To increase the accessibility of high-quality haptics, we designed a cost-effective actuation approach called the rotating motor actuator (RMA): it uses a small DC motor to generate vibrotactile cues on a rigid stylus. We conducted a psychophysical experiment where eighteen volunteers matched the RMA's vibration amplitudes with those from a high-quality reference actuator (Haptuator Mark II) at twelve frequencies from 50 Hz to 450 Hz. The average error in matching acceleration magnitudes was 10.2%. More current was required for the RMA than the reference actuator; a stronger DC motor would require less current. Participants also watched a video of a real tool-mediated interaction with playback of recorded vibrotactile cues from each actuator. 94.4% of the participants agreed that the RMA delivered realistic vibrations and audio cues during this replay. 83.3% reported that the RMA vibrations were pleasant, compared to 66.7% for the reference. A possible cause for this significant difference may be that the reference actuator (which has a mechanical resonance) distorts low-frequency vibrations more than the RMA does.

Construction of Ultrasonic Tactile Force Feedback Model in Teleoperation Robot System

The ultrasonic phased array as an emerging interactive tool is increasingly used for aerial tactile interaction. However, there is almost no method to achieve remote variable force feedback through the ultrasonic phased array as far as we know. This article presents a force tactile feedback method for teleoperating robot systems that tracks the five fingers and forms a focus on the fingertips. First, the perceived size of the focus depends on the input parameters. The influence of the parameters on the physical output pressure intensity was obtained through physical test experiments. Then, the absolute threshold and difference threshold of human perception were studied through psychophysical experimental methods. Finally, the input parameters were selected according to the experimental results. According to the collected data, the construction of the force regression model was completed, and different parameters were mapped to the perceived intensity. The contact force generated in the actual operation is fed back to the haptic system, and the constructed model automatically adjusts the control parameters to ensure that the user’s hand presents a sensory output corresponding to the intensity change. The entire force feedback system is evaluated, and results show that the system shows good perceptual quality.